Compositions of coated water-soluble polymers, their manufacture and their use to prepare aqueous solutions for use in enhanced oil recovery

Abstract

A solid composition of coated water-soluble polymer is made from 80 to 250 parts b.w. of solid particles of at least one water-soluble polymer coated with 100 parts b.w. of at least one paraffinic product solid at room temperature and whose melting point is preferably from 40° to 90° C. The solid composition is made by dispersing particles of the water-soluble polymer in the molten paraffinic product and then cooling down to room temperature.

What is claimed is: 
     
       1. A solid composition comprising solid particles of a water-soluble polymer coated with a protective coating consisting essentially of a paraffinic material which is a solid at room temperature, the amount of said protective coating being sufficient to protect said water-soluble polymer particles against humidity, agglomeration, microgel formation and oxidative degradation while nevertheless rendering said solid particles quickly dispersible in hot water, wherein said water-soluble polymer is polyvinyl alcohol, a cellulose derivative, a polysaccharide, polyacrylic acid, polymethacrylic acid, a polyacrylate or polymethacrylate salt, polyacrylamide, polymethacrylamide, poly-N,N-dimethylaminoacrylamide or an acrylamide-acrylic acid, ethylene-acrylic acid or styrene-maleic acid copolymer. 
     
     
       2. A solid composition according to claim 1, which comprises 80-250 parts by weight of said solid particles of a water-soluble polymer, and 100 parts by weight of said paraffinic material. 
     
     
       3. A composition according to claim 1, wherein the paraffinic material has a melting point of 40° to 90° C. 
     
     
       4. A solid composition according to claim 1, wherein said water-soluble polymer has a polyalkane backbone structure with a sufficient number of hydrophilic groups selected from carboxylate, sulfonate, amine, imine, ammonium, carboxamide, imide, hydroxy, acetyl, cetyl, carbamate and lactam groups to be soluble in aqueous medium. 
     
     
       5. A solid composition according to claim 1, wherein the water-soluble polymer is a partially hydrolysed polyacrylamide. 
     
     
       6. A solid composition according to claim 1, wherein said paraffinic material is a C 14-35  saturated aliphatic hydrocarbon, saturated aliphatic monoalcohol or fraction of low volatility from oil distillation. 
     
     
       7. A solid composition according to claim 6, wherein said paraffinic material is partially oxidized, hydroxylated or maleinized. 
     
     
       8. A solid composition according to claim 1, which further comprises 0.1-5 parts by weight of a non-ionic or anionic hydrophilic emulsifying agent. 
     
     
       9. A process for manufacturing a solid composition according to claim 1, comprising the steps of dispersing particles of said water-soluble polymer in said paraffinic material at a temperature higher than its melting point; and cooling the dispersion to a temperature lower than said melting point to form said solid composition. 
     
     
       10. A process according to claim 9, wherein a non-ionic or anionic emulsifying agent is further added to the paraffinic material in the dispersing step. 
     
     
       11. A process according to claim 9, wherein the solid particles of the water-soluble polymer are soaked or swollen with a polar compound selected from isopropanol, ethylene glycol, polyethylene glycol, glycerol and dimethylsulfoxide prior to dispersion in the molten paraffinic material. 
     
     
       12. A process according to claim 9, wherein the dispersion of the solid particles of the water-soluble polymer in the molten paraffinic material is poured into a mould before cooling. 
     
     
       13. A process according to claim 9, wherein the coated water-soluble polymer composition is extruded while still hot but after solidification. 
     
     
       14. In a method of producing thickened aqueous solutions for use in enhanced oil recovery, comprising dispersing a water-soluble polymer in an aqueous medium, the improvement wherein said polymer is dispersed in hot water in the form of a solid coated polymer composition according to claim 1. 
     
     
       15. A method according to claim 14, wherein the amount of said composition dispersed in said aqueous medium is sufficient to produce a concentration of the water-soluble polymer of 0.005-1% by weight with respect to water. 
     
     
       16. A composition according to claim 1, wherein said water-soluble polymer is polyvinyl alcohol. 
     
     
       17. A composition according to claim 1, wherein said water-soluble polymer is carboxymethylcellulose. 
     
     
       18. A composition according to claim 1, wherein said water-soluble polymer is hydroxyethylcellulose. 
     
     
       19. A composition according to claim 1, wherein said water-soluble polymer is carboxymethylhydroxyethylcellulose. 
     
     
       20. A composition according to claim 1, wherein said water-soluble polymer is a polysaccharide. 
     
     
       21. A composition according to claim 1, wherein said water-soluble polymer is polyacrylic acid or polymethacrylic acid. 
     
     
       22. A composition according to claim 1, wherein said water-soluble polymer is a polyacrylate or polymethacrylate salt. 
     
     
       23. A composition according to claim 1, wherein said water-soluble polymer is polyacrylamide or polymethacrylamide. 
     
     
       24. A composition according to claim 1, wherein said water-soluble polymer is poly-N,N-dimethylaminoacrylamide. 
     
     
       25. A composition according to claim 1, wherein said water-soluble polymer is an ethylene-acrylic acid copolymer. 
     
     
       26. A composition according to claim 1, wherein said water-soluble polymer is a styrene-maleic acid copolymer.